setup ssh vpn in one script

sslvpn.sh

#!/bin/bash

vpn_server=10.70.239.196
vpn_tunnel_id=8
vpn_ip_prefix=192.168.48
vpn_monitor_port=50008

ensure_tun_device() {
    local host=$1
    local device=$2

    device_info=$(ssh root@${host} -- ip -o link | grep -w "${device}")
    if [ -z "${device_info}" ]; then
        ssh root@${host} -- ip tuntap add ${device} mode tun
    fi
}

ensure_iptable_rules() {
    local host=$1

    iptable_rule=$(ssh root@${host} -- iptables-save -t nat | grep ${vpn_ip_prefix})
    if [ -z "${iptable_rule}" ]; then
        ssh root@${host} -- iptables -t nat -A POSTROUTING -s ${vpn_ip_prefix}.0/24 -j SNAT --to-source ${host}
    fi
}
start_sshvpn() {
    local device=$1

    autossh -M ${vpn_monitor_port} \
        -o PermitLocalCommand=yes \
        -o ServerAliveInterval=60 \
        -w ${vpn_tunnel_id}:${vpn_tunnel_id} root@${vpn_server} \
        -o LocalCommand="ifconfig ${device} ${vpn_ip_prefix}.2 pointopoint ${vpn_ip_prefix}.1 netmask 255.255.255.0" \
        "ifconfig ${device} ${vpn_ip_prefix}.1 pointopoint ${vpn_ip_prefix}.2 netmask 255.255.255.0; echo ssh vpn ready"

}

change_route() {
    ip r rep 10.0.0.0/8 via 10.70.238.1
    ip r rep default via ${vpn_ip_prefix}.1
}

device_name="tun${vpn_tunnel_id}"

ensure_tun_device localhost ${device_name}
ensure_tun_device ${vpn_server} ${device_name}
ensure_iptable_rules ${vpn_server}
start_sshvpn ${device_name}
change_route